The present application relates to a floating ball valve seat and, more particularly, to providing one or more resilient metal seals in a valve seat for a trunnion ball valve.
A ball valve provides a rotatable sphere, disc, or cylinder (generically the “ball”) in a flow path. The ball has a through hole that may be rotated into and out of alignment with the flow path to either allow or prevent the fluid to flow.
A conventional ball valve 10 is shown in FIG. 1. The conventional ball valve 10 comprises a valve body 12, a valve seat 14, a ball 16, a valve stem 18, and a handle 20. The ball 16 has a bore 22 extending along a diameter of the ball 16. As shown in FIG. 1, the ball valve is being rotated from the open position 26 to the closed position 28 by rotating the handle 20 a counter clockwise direction shown by the arrow 24. As shown, the ball 16 has been partially rotated and may be considered in a throttle position 30 although ball valves such as ball valve 10 are not typically used for throttling.
Conventional ball valves may be designed for lower or higher pressure operation. To close the flow path, the pressure of the fluid acts against the ball or the valve seat to push the ball and valve seat together to stop the flow. A high pressure ball valve is often designed as a trunnion ball valve. The trunnion ball valve allows for upstream pressure on the upstream valve seat 14-u to press against the ball 16. The pressure on the upstream valve seat 14-u allows for a leak path between the valve body and the valve seat. In certain applications, the valve seat 16 is designed as a floating valve seat. In these cases, a conventional compression spring may be provided between the valve body and the valve seat. The compression spring forces the valve seat away from the valve body, exasperating the leak path between the valve body and valve seat, and into a sealing relationship with the ball.
As can be appreciated from the above, the valve seat 14 and the ball 16 need form a sealing relationship to prevent leaks. The valve seat 14 and ball 16 are formed into a sealing relationship by a conventional lapping procedure. Lapping the valve seat 14 provides a ball seat that is perfectly spherical to match the curvature of the spherical ball. The lapping procedure is relative straight forward and convention, but adds costs to manufacturing of the valve.
Against the above background, it is desirable to provide an improved floating ball valve seat.